Shape optimization of a dielectric resonator for improving its unloaded quality factor

A novel approach for shape optimization of dielectric resonators is presented with an objective of improving their unloaded quality factor. Shape (level-set) and topology (topology gradient) optimization methods coupled with finite element method are utilized together, which as a result, relaxes the traditional trade-off made between the spurious-free band (isolation) and the high unloaded quality factor of the resonators. The defined cost function is minimized by the proposed iterative coupling between the level-set method and the topology gradient method. The optimized resonator, which improves the unloaded quality factor of about 65% compared with the reference, is then approximated for fabrication. The reference, optimized, and approximated resonators are fabricated and measured. Results from the simulated and the fabricated resonators validate the optimization approach presented in this work. © 2010 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011. © 2011 Wiley Periodicals, Inc.